Pension and Other Post-Retirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Post-Retirement Benefit Plans, Reclassification adjustments into earnings	$ 3.3	$ 3.5	$ 3.3
Defined Benefit Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1.9			$ 1.5	$ 5.6	$ 4.5
Interest cost	4.9			5.2	14.8	15.6
Expected return on plan assets	(6.4)			(7.1)	(19.3)	(21.4)
Unrecognized prior service credit	(0.3)			(0.3)	(0.8)	(0.8)
Unrecognized net actuarial loss	3.7			2.8	11.1	8.5
Net expense	3.8			2.1	11.4	6.4
Retiree Health and Life [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.1			0.0	0.2	0.1
Interest cost	0.3			0.4	1.0	1.2
Expected return on plan assets	0.0			0.0	0.0	0.0
Unrecognized prior service credit	(0.1)			0.0	(0.2)	(0.1)
Unrecognized net actuarial loss	0.0			0.0	0.0	(0.1)
Net expense	$ 0.3			$ 0.4	$ 1.0	$ 1.1